1. Field of the Invention
This invention relates to a salient pole dynamoelectric machine, and more particularly to a salient pole dynamoelectric machine whose stator and rotor can be separately cooled by means of a forced draft supplied from the respective exclusive blowers.
2. Description of the Prior Art
The conventional generator motor used in a pumped-storage power station is so arranged that cooling air is supplied to a stator and rotor by means of the same blowers; and hot air resulting from the heat expelled from the stator and rotor is cooled by air coolers, and circulated through the blowers to effect forced draft cooling.
Referring to FIG. 1, forced draft cooling blowers 1 fixed to a stator frame 2 introduce air into a housing 3 of a salient pole dynamoelectric machine in the direction of an arrow A shown in FIG. 1. Same portion of the air is conducted into spaces defined between the salient poles 4 of a rotor 5 in the direction of an arrow B. The other portion of the air passes through vent holes 6 formed in a rotor spider 7 and is brought into the rotor spider 7 as shown by an arrow C. Thereafter, this other portion of the air flows through radially extending air passageways 8 formed in a rotor rim 9 and then through the spaces defined between the salient poles 4 of the rotor 5 in the direction of arrows D. Thus, both portions of the air cool rotor coils of the rotor 5 and pole cores, thereby eventually cooling the rotor 5 itself to a desired level of temperature.
The air which has cooled the rotor 5 flows through an air gap 11 provided between the rotor 5 and stator 10 and flows into a stator air duct 12 in the direction of arrows E to cool the stator core and stator coils and eventually the stator 10 itself. Thereafter, the air which has now become hot is sent to air coolers 13 in the direction of arrows F. The hot air is cooled by the cooler 13 to a prescribed level of temperature and again enters a circulation route.
With the prior art salient pole dynamoelectric machine, however, the cooling air first flows through the rotor 5 and then through the air gaps 11 defined between the rotor 5 and stator 10 and is finally sent to the stator 10. Where, therefore, the rotor 5 gives rise to rotor loss in the air gap 11, the air is more heated by the extent of the rotor loss. After heated by the rotor 5, the cooling air flows through the stator 10 to carry away heat therefrom. Consequently, it has hitherto been necessary to apply a considerable amount of cooling air per second for thorough cooling of the rotor 5 and stator 10. The further disadvantage of the conventional cooling method is that since cooling air enters spaces defined between the poles 4 through various passageways, air stream conflict with each other, resulting in windage loss and consequently a decline in cooling efficiency.
Particularly with an ultra high speed large capacity generator motor in which the peripheral speed of the rotor exceeds 130 meters per second, it is necessary to apply a tremendous amount of cooling air per second. As things stand at present, however, it is impossible to provide an interpole space having a sufficiently large cross section to allow for the flow of such enormous amount of cooling air. Accordingly, limitation is imposed on the amount of cooling air which can be applied, probably failing to sufficiently cool the rotor and stator. As a result, the conventional cooling process further includes letting water streams flow in the rotor and/or stator for cooling. However, this arrangement complicates the construction of a cooling system, unavoidably rendering a dynamoelectric machine expensive and moreover possibly resulting in the serious danger of water leakage.